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湘西中-上奥陶统大田坝组喇叭角石科鹦鹉螺动物群及其个体发育

LITUITIDAE NAUTILOIDS FROM THE DATIANBA FORMATION(UPPERMOST DARRIWILIAN TO SANDBIAN,ORDOVICIAN)IN WESTERN HUNAN PROVINCE AND ITS ONTOGENICAL STUDY

【Author in Chinese】 方翔陈挺恩张允白李文杰张元动

【Author】 FANG Xiang;CHEN Ting-en;ZHANG Yun-bai;LI Wen-jie;ZHANG Yuan-dong;Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences;University of Chinese Academy of Sciences;Key Laboratory of Economic Stratigraphy and Palaeogeography,Chinese Academy of Sciences;

【Institution】 中国科学院南京地质古生物研究所中国科学院大学中国科学院资源地层学与古地理学重点实验室

【Abstract in Chinese】 中-晚奥陶世是鹦鹉螺类演化历史上的一个多样性爆发时期,其中喇叭角石科鹦鹉螺是该时期全球广布的重要类群。文中对产自湘西地区多个中-上奥陶统剖面的喇叭角石科鹦鹉螺进行了系统古生物学研究,特别对产自其中3个奥陶纪地层剖面的鹦鹉螺类进行了详细参数测量和形态分析,在此基础上开展了分类学研究,共描述了鹦鹉螺类2属6种(含1新种),包括Lituites lii Yü,Lituites ningkiangense Lai,Lituites anhuiense Qi,Lituites evolutus Fang,Chen and Zhang(sp.nov.),Cyclolituites hubeiensis Liu and Xu,Cyclolituites lynnensis(Kjerulf)。为了探讨Lituites的个体发育规律,文中在详细测量、统计了多块保存完整的标本的相关数据之后,采用了个体发育研究中的纵向分析方法,对Lituites的壳体扩大率和旋卷壳体部分的松紧程度进行了线性拟合分析,结果表明Lituites的发育阶段可以分为幼年期、快速生长期和成熟期三个阶段:幼年期主要对应旋卷壳体阶段,发育速度较缓慢;快速生长期为直壳阶段,生长速度较快;成熟期对应近住室部分的最后1—2个气室,具有隔壁变厚、气室变密等特征,指示个体完全成熟。

【Abstract】 In the transition of Middle to Late Ordovician,nautiloids had an explosive diversification,which is of great importance in its evolutionary history.It was in this period that lituitid cephalopods(Lituitidae)acquired its cosmopolitan distribution.Here we present our systematic studies of Lituitidae specimens from the Datianba Formation(latest Darriwilian to Sandbian) in the Mengxiaocun,Mayangcun and Yunpanta sections,western Hunan Province.Six species(including a new species)of two genera are described in detail,including Lituites lii Yü,Lituites ningkiangense Lai, Lituites anhuiense Qi, Lituites evolutus Fang,Chen and Zhang(sp.nov.),Cyclolituites hubeiensis Liu and Xu,Cyclolituites lynnensis(Kjerulf).The ontogeny of Lituites is studied and discussed in the present paper based on the measurements of the well-preserved specimens,among which a few are gerontic forms. The longitudinal analysis is adopted to describe the expansion rate of lituiticonic shell and coil index of coiled part,and the result of the linear fitting shows three characteristic developmental stages in the lifespan of an individual:(1)juvenile stage,corresponding to the coiled part;(2)rapid growth stage,typified by straight shells and rapid growth;and(3)mature stage,marked by shortened height of the last several camerae, which indicates a slowing down of growth rate by the body chamber.

【Fund】 中国科学院B类先导专项培育项目(XDPB05);国家基金委创新研究群体项目(41521061);国家重大专项(2013FY111000)联合资助;IGCP653项目“奥陶纪生物大辐射的启动机制”的阶段成果
  • 【CLC code】Q915
  • 【Downloads】58
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